Treatment of paper pulp



Patented Get. 4, 1927.

CLARENCE R. ROBINSON, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR TO ROBINSON FIBRE CORPORATION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA WARE.

TREATMENT OF PAPER PULP.

No Drawing.

This invention relates to the treatment of paperpulp stock.

In the preparation of paper pulp one of the principal objects is the complete separation of the fibres to form What is known as a free flowing pulp, so that in the subsequent forming operations the felted paper may attain a maximum strength and umformity. 'In, the manufacture-of sulphite and other chemically prepared pulps from wood, the liquor in which the chips are cooked, acts to remove the lignin and resin and other bonds for the fibers and thus leaves the fibres themselves free for the subsequent felting. In the manufacture of ground wood or mechanical pulp the grindstone acts to tear the fibres apart. Generally speaking the separation of the fibres in the chemical processes is more complete than in the mechanical so that paper made from the former isstronger than that made from the latter.

The chemical processes are, however, much more expensive than the mechanical so that in the cheaper papers, such as newsprint, mechanical pulp must largely predominate with a small addition of chemical pulp for strength. Improvements in grinding methods and machinery are making possible a better separation of the fibres and the production of improved ground wood papers, but the chemical pulps are still superior, largely because of the more complete separation of the 'fibres. Paper made from chemical pulps are superior to groundwood papers for the further reason that in the former the lignin and resin have been removed while they remain in the latter, slowly oxidizing and resulting in a yellow brittle paper.

I have discovered that the addition,-in the beater, of a small percentage of a sodium peroxide solution to any paper pulpenough to make the pulp react alkaline to litmusresults in a more complete separat'ion of the fibres and the formation of a stronger, tougher, cleaner, more uniform paper. Although this result is obtained Whenany pulp is treated, I realize the. most marked improvement in the treatment of pulp consisting largely or wholly of ground .wood either new or reclaimed.

In practicing the present invention I first make u an aqueous solution of sodium peroxide t e concentration of. which may range from 4% to 25%. This solution is then Serial No. 7,344.

added to the pulp in the beater or the solution introduced first and the pulp added to it. Sufficient sodium peroxide is used to turn the contents of the beater alkaline to litmus. *henworking with new stock, I have found that this alkaline reaction is obtained by adding from 0.1 pounds to 0.25

pounds of sodium peroxide to 100 pounds of pulp, all figured on dry basis. IVhen workmg With an average pulp in the form of reclaimed waste paper, I have found that from 1.25 pounds to 2 pounds of sodium peroxide per 100 pounds pulp should be added. hen Working with a reclaimed pulp made from arosin-sized paper with free alum present even more sodium peroxide must be used. In each case the sodium peroxide is added until the stock reacts alkaline to litmus. I have also found that better results are obtained if the temperature of the stock in the beater is from 120fto 130 F. Temperatures substantially above 130 F. are injurious to the fibres. After the beater is loaded with the pulp and the sodium peroxide solution, the contents are agitated to complete the separation of the fibres. This can usually be accomplished in from ten to twelve minutes.

- The resultant stock when discharged from the beater is perfectly free flowing and need not be passed through a Jordan engine. It is in fact much freer than it could be made by a Jordan. It is well-known that ordinary paper stock after standing for even a short while becomes unfit to form properly on the machine, whereas, stock treated in accordance with the present invention can or breaking test in favor of paper made' from the treated pulp. Such paper is also more uniform than paper made from untreated pulp, not only in thickness but in strength. It is also whiter when first made and, what is more important, remains white indefinitely and does not grow brittle and Week with age even thouglu largely or whollyemade from ground wood. ln'short, paper made from ground wood pulp treated in accordance with the present invention not only possesses many of the virtues of papers made from sulphite and other chemi ca pulps, but possesses these properties in a 'aration of the bres while maintaining the mixture at a temperature somewhat above usual atmospheric temperatures but insufliciently high to injure the fibres.

2. The method of treating paper pulp which comprises adding a solution of sodium peroxide to the pulp until the whole rea'cts alkaline to litmus, agitatingthe whole, and heating to a temperature not hlglier thanabout 130 F.

Y 3. The method of treating paper pulp which comprises adding a solution of sodium peroxide to the pulp until the whole reacts alkaline to litmus andagitating the whole for about ten minutesto complete the separation of the fibres.

4. The method of treating paper pulp which comprises adding a solution of sodium peroxide to the pulp until-the whole reacts alkaline to litmus and agitating thewhole to complete the separation of the fibres, while maintaining it at a temperature ap-' proximately from 120 to 130 F.

5. The method of treating paper pulp which comprises adding a solution of sodium peroxide to the pulp in proportions of from 0.1 pounds to 2.00 pounds of sodium peroxide to 100 pounds of pulp, dryweights, agitating for about ten minutes to complete the separation of thefibres, and heating to a temperature not higher than about 130 F. 6. The method of making paper which comprises forming a v pulp, adding a solution of sodium peroxide until the pulp reacts alkaline to litmus, agitating the pulp to separate the fibres, heating to a temperature not higher than about 130 F. and forming the paperinto webs or sheets.

7 The method of tre'atmg pulp in paper form which comprises adding a solution of sodium peroxide to the pulp until it reacts alkaline to litmus and agitating the mixture about ten minutes to separate the fibres.

8. Paper made-from a pulp treated with sodium peroxide until the pulp reacts alkaline to litmus, agitated about ten minutes to separate the fibres and heated to a temperature not'higher than about 130 F.

9. The method of treating ground Wood pulp which comprises adding sodium peroxide to the pulp until it reacts alkaline to ten minutes to comp ete the separation of the fibres.

10. The method of treating ground woodpulp which comprises adding sodium peroxide to the pulp so that it reacts alkaline to litmus, and agitatin the treated pulp about litmus,-agitat1ng the treated pulp to complete the'separation of the fibres and heating to a temperature not higher than about 11. Paper made from v ground wood pulp treated with sodium peroxide until the pulp reacts alkaline to litmus, agitated about ten minutes to complete the separation of the' fibres while heated to a temperature not higher than about 130 F.

In testimony whereof I aflix my signature.

CLARENCE R. ROBINSON 

